This invention relates to machines for sharpening knives and similar cutting tools, and deals more particularly with such a machine utilizing an endless belt.
Belt type abrading machines of the type having an abrasive belt and means for supporting and driving the belt along an endless path are well known, and it is also well known to use such machines for sharpening knives and other tools having elongated cutting edges. For a knife or the like to be optimally sharpened with such machines the edge must engage the abrasive belt at an appropriate angle and with an appropriate amount of force. During the sharpening procedure heat is generated at and near the area of co-engagement in rough proportion to the force existing between the edge and the abrasive belt. If the force is too great the edge becomes too hot and the resulting change in the microstructure of the knife material makes it less tough and less able to keep a keen edge, and the belt wears rapidly. On the other hand, if the force is too little the sharpening procedure may require an undue amount of time. Also, for best cutting results the two surfaces of the knife which meet to form the cutting edge should have an angle relative to one another falling within a narrow range, making the position of the knife relative to the belt quite critical.
To aid in the proper positioning of and the application of proper force to a knife being sharpened it is known to use a rest having a guide surface inclined to the path of travel of the belt and to mark, usually by trial and error, an index mark on the surface indicating the point to which a knife is to be moved for sharpening. However, this does not preclude the possibility of the knife being accidentally or intentionally moved beyond the index mark and creating overheating and other problems.
It is therefore the object of the present invention to provide a simple, easy-to-use and inexpensive machine for sharpening knives and other cutting tools which provides for the proper positioning of the tool relative to the abrasive belt and which also provides a relief mechanism assuring that a tool cannot be advanced into the belt too far or with too much force during a sharpening process.
Other objects and advantages will be apparent from the following description of a preferred embodiment of the invention and from the accompanying drawings and claims.